NASA DC-8 airborne cloud radar: Design and preliminary results

The University of Massachusetts Microwave Remote Sensing Laboratory and NASA Jet Propulsion Laboratory have developed a 95 GHz airborne radar system for remote sensing of clouds. This instrument was recently operated aboard NASA's DC-8 Airborne Laboratory and participated in the Cloud Layer Experiment (CLEX) in the central U.S. and in the Southern Alps Experiment (SALPEX) in New Zealand. The development of this system was motivated by the need for a sensitive, well-calibrated millimeter-wave cloud radar that can probe clouds from above. This geometry avoids the attenuation suffered by ground based systems that look up through precipitation and also simulates the viewing geometry of a spaceborne sensor. This paper describes the design and operating characteristics of the instrument as well as preliminary results from the initial deployments. Engineering test flights were conducted during June 1996, concurrent with CLEX. The instrument also collected data during two flights from California to Hawaii and New Zealand and another flight near New Zealand. Data from the flights are used to demonstrate the instruments capabilities. The data from both experiments are classified into the four classes of cloud systems used by the GEWEX Cloud System Study (GCSS). Reflectivity statistics for each class of cloud system are presented.